Either way, netstat -nlp isn't lying about who owns the port 80 socket. It's a terrible idea, but the data returned is not incorrect.
In other cases, Systemd acts as an advanced xinitd and start services on demand, which means that Systemd listens and starts a service, but the service does the accept and responds.
So... it's hard to say without digging into the systemd configs.
Nope, systemd only opens the socket and passes the fd to Apache.
> Or is it launching Apache on demand like some sort of advanced inetd?
Yes. Since it's already init's job to start services, it does not make any sense to have a different system to start socket-activated services.